Green steam

Energy & Sustainability
Green steam

Our pal I-Wei Huang, of Crabfu SteamWorks, sent us a link to this “green” steam engine, a super-efficient two- (or more) piston engine that is allegedly easy and economical to build. It has a very ingenious way of converting reciprocating movement into rotary movement, the action of which you can see in an animated GIF on the site. It’s amazingly efficient, (freewheeling at a mere 2 psi).

Green Steam Engine Home Page – Link

82 thoughts on “Green steam

  1. MrH says:

    1. Most small scale steam engines will run on very little pressure with no load. Some simply by blowing into the intake pipe.
    2. I can not see where the inventor has reduced the parts count – a “normal” steam engine has a piston/Flywheel/Connecting rods etc. In this case he has 2 pistons & cylinders, An extra flexy rod that must absorb some power as well as complex joints that move and pass steam.

    3. I can not see how this arrangement is more compact – if you remove the boiler most steam engines are very compact unless toys and a turbine even more efficient and compact.

    No I am afraid it is interesting but not the solution to the worlds energy problem.

  2. JeffTheBaptist says:

    I have to agree with MrH. To steal his format:

    1) This design has a lot of moving parts. The flexy rod is constantly moving and, more importantly, deforming. The cylinders themselves are in motion. All that energy has to come from somewhere. In a traditional reciprocating steam engine, only the pistons, pushrods, and crank move. This is a good thing.

    2) I can’t see scaling his technology up to anything of useful size. One of the reason this thing works is that all the moving parts are lightweight and small because of scale. Once it gets bigger, everything will become relatively heavier (due to scaling) and the masses will matter. The vibration and motion of those cylinders will be important. The large deflections the flexy rod will cause fatigue problems. All those complex articulated joints won’t hold up as well either.

  3. garethb2 says:

    These are really good comments, and reveal my relative ignorance about engines — although a lot of what you both are saying is just good mechanical sense (when ya think about it).

    I’d love to hear how the builder would respond. Maybe I can get him over here.

  4. garethb2 says:

    I sent Roger Green email about this item and discussion…

  5. JohnnyGTO says:

    Isn’t a turbine the most efficient way to use steam, only one moving part?

  6. Crabfu says:

    I love seeing people making a twist on something old. Maybe it’s not better than traditional piston engines, I dunno… maybe it will someday? I dunno, but worth exploring a bit don’t you think? Just the fact that he approached it from a different angle is worthy of a make blog post! I applaud Mr Green for thinking outside of the box, and able to pull it off!

    It’s just so mesmerizing to watch….

  7. samurai1200 says:

    I was really curious how this thing was going to operate, and suspected something fishy when there was a mention of an animation of it… what could possibly so interesting about the movement of a steam engine?

    Besides everything else the above has mentioned (which are all completely valid), wouldn’t this engine just rattle itself apart eventually? There doesnt seem to be a counterweight providing any balance to the lateral rotation of the system being made possible by that nice flexy-tube-shaped thing in the center…

  8. 3Newton says:

    It is all very nice that the author states that is efficient, but what does this mean? Which size engine achieves which efficiency?10%? 20%? 99%? 100%? (we all have heard this recently ;-)
    Without this information the site is useless. What should I buy a licence when I don’t even know the key technical parameters?

  9. amp2003 says:

    I fail to see the problem with having a flexible rod as part of the design. Sure it takes energy to deform it, but that energy is later returned to the system. It’s not like you’re loosing anything here.

  10. Tercero says:

    I read a few reviews on this, and it sounds like it’s a death trap waiting to happen. If you build it be careful of the shrapnel when this thing tears itself apart. Anyhow, wouldn’t it be easier just to make a Tesla turbine and vent steam through it?

  11. chezgreen says:

    The reason for the improved efficiency of this flex rod mechanism is that it produces intermittant straight line movement. There are no side forces as in a typical crank mechanism. This means that the cylinders do not require lubrication and the valves do not need a separate mechanism to operate. The pistons are sealed with “O”rings. There is virtually no wear. In a normal engine the pistons are either pushing against one side of the cylinder or the other causing friction. The flex rod mechanism does not take energy because it is like a spring that gives back as much as it takes when it returns. The purpose is to maintain alignment of the cylinders. A six cylinder uses the same number of crank bearings as a one cylinder engine (one). Because the engine is not made from large castings,it looses far less heat. The glass cylinders do not conduct heat like metal. One of these engines has been made that produces 800 HP. It is very light-weight and requires far less steam than a normal engine. It is also very cheap to build. The engine that is in the plans(a DIY version) may be assembled in five minutes. The exhaust is pure distilled water without any contaminants. The water can be recycled back to the boiler without gumming up the boiler with minerals and oil.
    Turbine engines require high volume superheated steam. The vanes have to be changed often at great cost. My engine runs on saturated steam that operates on very simple and safe boilers that usually do not have to be certified. A Tesla engine produce very little torque and is high mantenance. The small green engines run 5000 RPM”s and up. None have come apart. The reason is the straight line movement. Your concern about this is unfounded in fact. There are many hundreds of these engines in use all over the world. I have never heard of one flying apart. There are three companies that are in the process of manufacturing this engine in different forms and sizes. You will see them on the market soon. I doubt that they would want to manufacture something that flies apart. Regards, Robert Green

    1. galapoola says:

      Do you have a list of the manufacturers you mention who are currently building your design? How about hobbyist or steam enthusiasts, any with a working unit? We are all intrigued by the technology and the videos but there seems to be no other information on the web other than your own and on forums such as this. We never see your design under load, have you ever put a belt to those pulleys and done some work?

  12. Tercero says:

    $45 is a bit steep for the plans, and a Tesla turbine has one moving part. Where’s the high maintenance? Sorry, but the flex rod thingy looks like an accident waiting to happen. Hence, why it’s not used in modern engine.

  13. chezgreen says:

    Where is the Tesla engine being manufactured? About the one moving part that Tercero is referring,- that’s the part that goes.The blades burn out in a flash. Steam is very corrosive. What makes you think my engine is not being used? What accident is supposed to happen with the “flex rod thingy”? Those flex rods are used in heavy industry every minute of the day. 360 days a year at thousands of RPM’s per minute.

  14. wiml says:

    Tercero: Tesla turbines are neat, and really easy to build, but wouldn’t they be pretty inefficient? It seems to me there’d be a ton of energy lost in that boundary layer. A traditional reaction turbine should be more efficient, at least at its design speed.

  15. Fizzgutss says:

    I’m building a Green Flexrod engine for a friend it’s rubbish as are the plans and claims. Complete LIES re 800hp engine and 5 minute assembly.

  16. justsaying says:

    This engine would be more interesting if it was a stirling engine? Water and Fire are limited resources. Energy should not compete with food or water.

  17. ablackstormy says:

    The supposed adantage of the Tesla bladeless turbine over reaction turbines is that the Tesla design does not require superheated, high-pressure dry steam. For the hobbyist/tinker this is a real bonus, as it decreases the likelyhood of a catastophic failure in the boiler and associated plumbing.

  18. Dana says:

    I think it’s brilliant. We need more people like this who put forward new things – that’s the only way progress is made. Constructive criticism is good, but those who just posted negative unfounded comments appear a little jealous…

  19. dr01allen says:

    It’s amazing to see how those who can’t do it easily criticize those who have done it.

  20. will says:

    Has anyone out there built one? I would like to hear from them.

  21. Anonymous says:

    I think the draw of green’s steam engine is that it supposedly works on relatively low prssures…20 psi! That’s about what a pressure cooker gets to.

  22. Fizzguts says:

    Quote “It’s amazing to see how those who can’t do it easily criticize those who have done it.’
    It’s amazing to me that those who don’t have a clue about the technology are always the most fervid supporters.
    To repeat the claims are rubbish, the plans are rubbish and I wish I’d never offered to make the damm thing. If you don’t have a lathe and a silver soldering rig, you cannot build the unit. There is a huge amount of stuffing around required.

  23. Snoopy22 says:

    Well, as a matter of fact, I have made two of these engines. Yes, both of them required fine tuning but, worked beautifully after some TLC and deicated tweaking. Bottom line, either your heart is in it or you are wasting your time and ours for complaining about something that you haven’t followed through with.

    Robert has improved on his plans and construction ideas. As a result his engines appear even better. No! I have not built one of them yet but I probably will in the near future.

    It’s more fun excerzing my mind and making it work than working my jaw muscules and complaining.

    1. galapoola says:

      I’m sorry but you wrote in the same post:
      “Well, as a matter of fact, I have made two of these engines.” and then “No! I have not built one of them yet but I probably will in the near future.”
      Not sure where that puts things. If you’ve built one can you tell us a bit about it. The consensus online seems to indicate that no one other than the inventor has built one.

  24. bob says:

    Pretty cool that the inventor posted here. But, I have searched for and wide for one single other person who has built the green steam engine… I have yet to find any pictures on any other website then the inventors.

    I have also heard that the engines are being mass produced by a big company. That was about a year ago.

    Now… From the videos, the engines appear to work.

  25. nieves says:

    What kind of joint are the pistons connected to that allows them to swivel around like that? The joint would also have to hold pressure. I don’t think I see it on the inventors website in the “harder to find” parts section.

  26. jober says:

    Is there a way I can contact you?
    I have the plans in my hand and I’m hoping you can answer some questions.
    I would ask Robert but the fist rule is don’t bombard your guru with a bunch of stupid little question, save him for the big ones.
    Please don’t take that statement to mean your not a guru ether. ;)
    I seem to have to much time and to much money!

  27. M.A. Ray says:

    I have been working for six months to get it to work from the incomplete plans I got from Mr. Green. I still have not got it to work. Do not waste your money.

  28. Anonymous says:

    “Do not waste your money.”
    LOL, But wasting money is what I’m good at.
    It’s not finished but I will let you know when it is.

  29. Dexter says:

    Has anyone seen this unit in action, or found a reference to this engine being used in the real world? I see comments about it being trash, a death-trap, and something about reading reviews (which I’ve been unable to find myself online). I have the resources to easily build a small unit, but want to see it in use or recieve a testimonial from someone other than the inventor before I put my time and effort into it.

    I’ve had a very qualified mech-eng look at the plans and while the detail of the plans and robustness of the unit is in question, he thinks it’ll work if properly engineered carefully. Constructive thoughts from anyone?


    1. galapoola says:

      I’ve tried to contact Mr. Green via his web site email and haven’t heard back. All of the videos online are his so there are no video examples of plan built units out there. Maybe you can be the first to build one from plans and then tell us all about your experiences. I’ve yet to see one under load so I’m not sure if any of the claims for HP are valid. The videos all show a free spinning unit not performing any work.

      1. Dexter says:

        Yep, I’m afraid I’ve had the same problem. I’ve only had a response when enquiring about buying the plans or gotten the same rhetoric about them being mass produced and the small unit producing 7 hp. This was a couple of years back and still nothing to show for it. It’s a real shame that Mr. Green doesn’t appear to be willing to show an application of the engine in use under a decent load or in an industrial application. I’d love to build this and have the capabilities to build a unit to good tolerances even without complete dimensions on the plans supplied, but just can’t justify the time and expense without knowing that this will work for my application (4-5 Hp steam vehicle).

        Mr Green, if you’re reading this, please clue us in. If someone builds this and it works, I guarantee positive news will spread pretty quickly, and you’ll get the publicity you deserve. But from what I’ve seen online, no-one has a clue whether it works as claimed and most people are extremely skeptical on every forum I’ve read as it’s not been seen working under load.

  30. DM says:

    Go to greensteam engine to view the 2 new ones made from a small CNC shop. The 2 and 4 cylinder are both precision machined and run smooth. A 6 cylinder version(not shown yet) is also running under steam power, altho the boiler is not quite up to “steam” yet but but their progress with the boiler is improving.

  31. Mike says:

    Another manufacturer: Near Futures Energy Corporation

    Also, I’m building this engine and I do not see what people are belly aching about. This concept is mechanically sound. I am making a few modifications on mine, but the design in the plans really isn’t worthy of all this negative attention. I will say, that the plans aren’t more than a few detailed drawings and photos. There is no step by step instruction. This is the only disappointment I have found. I have contacted Mr. Green for help via email and received it within a couple of days.

    I think we have fear mongers on here. Why? Throughout time people have opposed new inventions and claimed they would fail. I for one would rather try things out for myself and then formulate my opinions based on facts.

  32. Anon says:

    Anyone have any progress backing up Mr Green’s engine?

  33. Anonymous says:

    Been following this for awhile. Has anyone had any luck using it in a “real world” application?

  34. galapoola says:

    I received an email from a fellow who at one time was responding for
    Looks like he is trying to sell turn-key units, here is his email pitch:

    HIL GreenPower, Inc.
    13844 Alton Parkway
    Irvine, CA 92618 USA
    949-297-4861 949-297-4897 Fax

    Fully assembled Green Steam Engines are now available.

    We are offering the 2 cylinder, 10 hp engines for sale at $1,500 each with a 90-day money back guarantee.

    light weight
    industrial grade
    uniquely designed
    few moving parts
    no lubrication required
    disassembled and reassembled in under an hour

    The only regular maintenance requirement noted to date is the replacement of piston O-rings. This can easily be completed in about 15 minutes, and replacements are available from HIL GreenPower, Inc


    Each engine weighs about 25 lbs.; dimensions, with the drive shaft, are 21”L x 8”H x 13”W. Materials are brass, aluminum and stainless steel to prevent corrosion. The engine may be installed in any position and uses approximately 22 cubic inches of steam per revolution. It yields about 10 hp from 100 psi of steam at 300 rpm’s. Optimal operating range is from 200 to 600 rpm and 60 to 150 psi.


    For the full 10 hp from this engine, we recommend using a boiler in the range of 2.5 to 5 boiler horsepower capable of producing 100 psi to power this engine. Lower pressures may be used for applications requiring less horsepower. Speed is controlled by a simple ball valve.

    To order your 10 hp 2-Cylinder Green Steam Engine, complete the attached Order Form and forward to

    For more information, email


    I wrote him back but no response, still want to see/hear about an end-user. Here’s my email back:

    Thanks for writing and the very best on your business venture. is parked and not an active website.
    Do you have any further information?
    There is very little out there on this fascinating steam engine.
    I participated on a few forums and even read some of Mr.Green’s entries.
    The consensus among the folks participating was not optimistic.
    One theme never really addressed is who has one of these units up and running in any application.
    Mr. Green made one entry and was never heard from again.
    I for one would love to hear a customer testimonial or see the 10 HP unit you have for sale installed and working.
    All of the videos on Mr. Green’s site seem to be free wheeling.
    The possible exception is the one generating power to light a very small automotive type bulb, not very impressive.
    All the best,

  35. galapoola says:

    Found two videos with Green Steam engines that are “not” from the inventor, for your viewing pleasure:

    at about 1:17 in

  36. ScaryDAve says:

    All engineering talk aside, I still think this thing is most likely a sham/toy but I did come across the video below. Comments disabled and no way to read what it’s putting out wattage or HP wise. Nor is there a way to see what pressure is going in or what RPM it is running at.

    As a former special effects guy, my experience is, if it works, people use it. If you can’t find anyone bragging about how well it works and showing it off, it’s because it doesn’t make them feel cool. In other words, it’s junk.

    I would love for this to be real but it seems like nothing more than a toy thus far.

    In this this previously posted video, of the same POS machine failing to perform well, is another machine made of a hydraulic ram and valve which seems far more interesting.

    Sorry to sound pessimistic but after all these years, if this worked, it would be a no brainer for sale in the back of popular mechanics and a hundred other places including ebay.

    My interests are strictly generating electricity and heat in a remote location. I don’t see this doing so anywhere.


    1. Nicko says:

      Hello DAve,

      You said that your interests are generating electricity and heat in a remote location. I also have the same interests. I want to built a parabolic solar system and use some kind of steam engine. My system want to be able to produce about 1kw electrical power. Do you have something to suggest me? Which steam engine stould i use? Also how can i make a boler?



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Gareth Branwyn is a freelance writer and the former Editorial Director of Maker Media. He is the author or editor of over a dozen books on technology, DIY, and geek culture. He is currently a contributor to Boing Boing, Wink Books, and Wink Fun. His free weekly-ish maker tips newsletter can be found at

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